The present invention relates to a fan arrangement, in particular to a cooling fan for an engine system of a motor vehicle.
Axial ventilator fans have rotatable blades which are connected to form a fan wheel. In operation, a negative pressure is generated on an inlet side of the blades and an overpressure on an outlet side of the blades, leading to an air flow through the fan in a substantially parallel direction with respect to the axis of rotation of the fan wheel.
When used as a cooling fan for an engine system, the fan is arranged close to an engine block, whereby the air flow conveyed by the fan rebounds and is discharged towards the side, that is, transversely to the axis of rotation, of the intervening space formed by the engine block and the fan. Furthermore, because of the pressure difference between the inlet side and the outlet side, a reverse flow occurs close to the outer end of the blades, reducing the efficiency of the fan and leading to undesired pressure loss and noise generation.
In addition, turbulence can occur in the region of the lateral outflow from the intervening space between engine block and fan, leading to a pressure rise in the intervening space and impeding the discharge of the air. The efficiency of fan performance is thereby further reduced.
A fan arrangement comprising a fan wheel having at least one blade is known from U.S. Pat. No. 6,599,088 B2, the blade being located in an annular element which has a flared inner outflow surface with a shroud. The collar on the outflow side of the shroud has a radially outwardly directed edge surface which represents an extension of the flared inner outflow surface.
The above fan arrangement provides a special outflow geometry of the annular element. Furthermore, the edge surface of the shroud must be aligned with the geometry of the annular element. This increases cost and complexity in the manufacture of such a ventilator fan.
The document U.S. Pat. No. 7,478,993 B2 discloses a ventilator fan having fan wheel blades, the outer ends of which are connected to an annular element. The fan wheel moves inside a shroud extending beyond the fan wheel on the outlet side and having a coanda ring which extends radially inwards from the shroud on the outlet side of the fan wheel and has a flow-guiding contour in order to avoid as far as possible turbulence at the side of the intervening space between engine block and ventilator fan.
However, the provision of the coanda ring on the outlet side of the fan wheel increases the overall height of the ventilator fan, which is disadvantageous for use in the engine compartment of a motor vehicle. In addition, this solution is very susceptible with respect to component tolerances. Even small tolerance fluctuations lead to a deterioration of efficiency.
Furthermore, a device for controlling the flow through a fan arrangement in which blades are arranged adjustably in an annular element is known from the document U.S. Pat. No. 7,992,664.